In this study, oxidized iron particles on an amorphous carbon film were irradiated by an intensive and convergent electron beam in situ inside a transmission electron microscope. It was found that some iron particles could be fractured into several particles and also could form a graphitic film on the outer surface in a very short time by the electron beam. By the electron beam the iron particles were found to be reduced to alpha-Fe, gamma-Fe, or Fe3C. The high temperature phase of iron (gamma-Fe) was observed to be stable only when it was tightly encapsulated in a graphitic film formed during the beam irradiation. This result indicates that the high elastic modulus of graphite on the surface holds the gamma-Fe phase from expanding and transforming to alpha-Fe (the stable phase of iron at room temperature). (C) 2004 Elsevier B.V. All rights reserved.